The invention relates to apparatus for clamping at least one non-woven or paper sheet and use thereof in converting the sheet into finished products once the sheet has been manufactured by a wet or dry process.
More specifically, the invention relates to apparatus for clamping at least one non-woven or paper sheet and includes two substantially mutually tangent cylinders between which the sheet is made to run. In this apparatus, at least one of the cylinders, on its surface and in a zone that makes contact with the sheet, is fitted with a clamping band having first salient elements. The interaction between the two cylinders during their rotation in the presence or absence of a sheet subtends an active surface. This active surface is described in greater detail below.
Herein the term xe2x80x9cpaperxe2x80x9d denotes any product based on paper fibers, for example tissue paper and absorbent paper products made by either a dry or wet process. As regards the latter, the paper fibers are bonded by a thermoplastic bonding agent, such as latex or heat-melting fibers. Some paper products also may be composed of cellulose fibers other than paper fibers and on occasion the paper products may include some synthetic or artificial fibers.
The invention also covers non-woven products.
The invention furthermore applies to making tissue paper goods and, in particular, paper napkins, handkerchiefs, paper towels, sanitary paper or the like.
In general, these goods are made from one or more superposed paper plies that are subjected to clamping. There can be several purposes for such clamping.
As shown further below, the clamping action applied to one or more plies between two preferably oppositely rotating cylinders of the apparatus, as a function of such operating conditions, in particular as pressure, and the kind of cylinders involved, can entail the following:
plain joining of the plies to each other, whether or not additives are used,
depositing an additive on the surface of one ply, for example applying adhesive, ink, lotion or the like,
marking one or more plies running through the apparatus.
The expression xe2x80x9cplain joiningxe2x80x9d herein denotes that several plies are mutually attached by mere pressure, with or without adhesive. In case adhesive is used, the apparatus is fitted with an engraved cylinder and a mating cylinder which is the adhesive-bearing and depositing cylinder.
Herein the expression xe2x80x9cmarkingxe2x80x9d denotes any kind of deformation of the non-woven or paper sheet that might be implemented by running the sheet through two cylinders of which one at least is fitted with a clamping band. By clamping the paper sheet against the surface of a mating cylinder, the clamping band causes the sheet to be marked either by compressing the paper fibers (xe2x80x9cmarkingxe2x80x9d in the rigorous sense), or by deforming into salients (embossing) in patterns which correspond to salient elements configured on the clamping band.
Depending on apparatus application, the clamping band imparts a pattern, which is permanent or not, to the non-woven or paper. At the time the cylinders are in mutual contact by means of the inserted non-woven or paper sheet, any applied pressure will entail marking by the clamping band. The magnitude of this pressure (relatively weak if two plies are combined) may be such that this marking will be slight and impermanent. In such a case, generally no marking at all will be visible on the finished product. At high pressure, marking will be permanent and visible on the finished product.
The clamping band includes first salient elements engraved on its cylindrical surface. These elements can be configured in such a way that they constitute one or more, continuous or discontinuous salient zones around the cylinder. The elements can be geometrical or not. The elements can be discrete, for example dots or dashes, or the elements can be continuous or discontinuous lines, or otherwise. Patterns also can be subtended by an absence of salient elements or tips. For that purpose, tip-free zones in a desired pattern on the paper are present on a surface otherwise containing a regular array of tips.
Depending on what kind of mating cylinder is used and the pressure applied by the cylinders on the paper sheet, different kinds of markings can be implemented.
Accordingly, the cladding of the mating cylinder can be a relatively flexible material when compared with the cladding of the cylinder bearing the clamping band. Also, the mating cylinder can be made of any material which is similar to that of the clamping-band bearing cylinder. The external cylindrical surface of the mating cylinder can be smooth and also can be fitted with hollow elements complementary to the clamping band""s salient elements. Moreover, the external cylindrical surface of the mating cylinder can be fitted with salient elements which are identical with those of the clamping band in such a way that the paper sheet is clamped at a given pressure between two mutually opposite salient elements.
Depending on these various parameters, the kind of marking used may entail different effects, in particular increasing the paper thickness (embossing), increasing the paper""s absorption, interlinking the various plies resulting in forming the sheet of paper, an especially aesthetic marking but also a decrease in paper thickness (marking in the rigorous sense) in the pattern zones.
In all cases, the paper sheet is clamped between two cylinders of which the axes run substantially parallel and which are made to approach each other radially and which are driven into rotation once the sheet of paper runs between them.
Accordingly, the paper is clamped in the cylinders"" contact zone.
In theory, this contact zone is a line running parallel to the axes of rotation of the two cylinders, but in practice the contact zone assumes a certain width depending on the cylinders"" circumference (diameter) and width, the compression they exert, the features (thickness, hardness, etc.) of the cylinder claddings and the features (thickness) of the clamped non-woven or paper. As a result, the zone constitutes a contact strip running axially along a main contact generatrix. This zone is not necessarily regular width-wise. The zone can be rectangular, centrally concave or convex, etc. This pinching zone in the form of a contact strip between the two cylinders is generally called by the English word xe2x80x9cnipxe2x80x9d.
Be it borne in mind that when the thickness of the non-woven or paper sheet is greater than the inter-cylinder gap, the nip also may be present between the cylinders and contact set up through the intermediary of the sheet.
With or without the sheet between them, the two cylinders interact during their rotations and subtend an active surface subtended by the salient elements arrayed on the cylinder surfaces. More specifically, the active surface of the clamping band includes the surface of the salient elements which by means of the sheet make contact with their mating part and, in some cases and in particular if the mating part is made of rubber, in contact with the surface of part of the zones situated between the salient elements, where the zones on account of the deformation of the mating part and of the paper also can make contact by means of the sheet of paper with the mating part. In the latter case, the applied pressure varies between the peaks of the salient elements and the contact zones between the salient elements.
An active surface which is termed the xe2x80x9cinstantaneous active surfacexe2x80x9d is associated with each nip.
Accordingly, the consecutive instantaneous active surfaces by means of which the two cylinders cooperate with one another vary as a function of the salient elements of the clamping band and, furthermore, as a function of the area of the contact zone (nip).
FIGS. 2 and 3 show two illustrative configurations of salient elements for a clamping band.
FIGS. 2 and 3 show two defined bands B1 and B2 representing the contact zones of two cylinders at two of their angular positions.
In the example of FIG. 2, and looking at the contact zones B1 and B2, the instantaneous active surface of the band B1 is identical with that of the band B2.
In the example of FIG. 3, the two bands B1 and B2 exhibit two much different consecutive instantaneous active surfaces because, unlike the case for the band B1, the surface of the salient elements of the band B2 is zero.
In case the cylinders exert compression work and as regards these cylinders"" angular position corresponding to the band B2, interaction takes place between these two mutually contacting cylinders, but this interaction is much different from that of these same cylinders in the angular position corresponding to the band B1. Accordingly, in the configuration of the salient elements of FIG. 3, the stresses undergone by the cylinders vary substantially in time when these cylinders are rotating.
Such varying interaction stresses on the two cylinders which implement clamping substantially degrades the mechanical strength and service life of these cylinders and of any apparatus in general (vibrations). This problem arises in many apparatus which clamp a non-woven or paper sheet between two cylinders of which at least one is engraved.
Accordingly, it is an object of the invention to improve apparatus clamping a non-woven or paper sheet and offering longer service life of the cylinders and the overall equipment. Another object of the invention is to create widely varying patterns on the sheet by eliminating any constraints regarding the regularity of interaction between the cylinders due to the salient elements, whereby pattern selection would be reduced.
Accordingly, it is henceforth possible to select different shapes, distributions and density patterns.
For that purpose, the invention provides a non-woven or paper clamping apparatus of the above described kind which is characterized in that at least one of the cylinders is fitted at its surface and in a zone designed to be in contact with the other cylinder through an intermediary or not of the sheet with a load-compensating band including secondary salient elements, the band being selected in such a manner that the consecutive instantaneous active surface variation of the clamping band and of the load-compensating band is less than the variation of the consecutive instantaneous surfaces of the single clamping band.
Other features of the invention, whether considered singly or in combination, include the following features:
variation among the consecutive instantaneous active surfaces of the clamping band and the load compensating band is substantially zero,
the width of the active surface corresponding to the single load compensation band varies along the circumference of the cylinder on which this band was created as a function of the instantaneous active surface of the single clamping band,
the two cylinders rotate in mutually opposite directions,
the first salient elements of the clamping band are identical with or different from the second salient elements of the load compensating band,
the load compensating band is configured on one cylinder outside the clamping band,
the second salient elements of the load compensating band are different from the first salient elements of the clamping band and the load compensating band at least partly straddles the clamping band,
at least one of the cylinders bears at least one clamping band and at least one load compensating band,
the height of the load compensating band""s salient elements is substantially identical with the height of the clamping band""s salient elements,
the height of the load compensating band""s salient elements is greater than the height of the clamping band""s salient elements,
the height of the load compensating band""s salient elements is less than the height of the clamping band""s salient elements,
the load compensating band includes a rolling zone which determines a minimum width of the active surface of the load compensating band,
the rolling zone of the load compensating band is radially configured at the same place as the remainder of the load compensating band,
the rolling zone of the load compensating band is configured radially outward from the remainder of the load compensating band,
the rolling zone of the load compensating band is configured radially inward relative to the remainder of the load compensating band,
several load compensating bands are fitted on the same cylinder,
each load compensating band includes one rolling zone.
Furthermore, the invention also relates to a cylinder clamping a non-woven or paper sheet, which is characterized in that it includes a load compensating band defined by one of the above features.
Also the invention relates to equipment including at least one apparatus defined by any of the above features.
Further, the invention relates to a method combining at least two non-woven or paper plies and characterized in that it includes the operation of apparatus having any of those features, wherein the sheets are clamped between the two cylinders near the clamping band in the presence or absence of adhesive.
The invention also relates to a marking procedure applied to at least one non-woven or paper sheet which is characterized in that it operates apparatus with the same features wherein the clamping band imparts a pattern to the non-woven or paper sheet by deforming this sheet clamped between the two cylinders.
The invention also relates to any procedure using the apparatus of the invention to apply additives to a non-woven or paper sheet.
The invention also relates to a procedure for manufacturing tissue paper articles which include at least two plies and is characterized in that the plies are mutually joined by marking, embossing or combining.
Lastly, the invention provides a non-woven or paper article including at least one ply and characterized in that it is marked using the above marking procedure.